When the Greek poet Homer was writing The Odyssey around 2,800 years ago, the Earth went through an abrupt period of cooling, caused by the sun - and the same could happen again soon.

Scientists at the GFZ German Research Centre for Geosciences analysed lake sediment in Lake Meerfelder Maar, and found direct evidence of a sudden cooling caused by a 'solar minimum'.

Some scientists suspect that the current period of high solar activity - including increased sunspots and solar storms this year - will be followed by a 'minimum' period, which could even cause an Ice Age.